Abstract 10253: Sin3a Gene Delivery Restores Bmpr2 Expression Through Foxk2 in Pulmonary Arterial Endothelial Cells and Inhibits Sugen/Hypoxia-Induced Pah

Abstract

Background: Pulmonary arterial hypertension (PAH) is a fatal lung disease of multifactorial etiology, with no curative treatment. Several studies have previously suggested that the loss of BMPR2 expression is associated with a severe hemodynamic profile and poor outcomes in PAH patients. Furthermore, preclinical studies showed that the loss of BMPR2 function is sufficient to induce a PAH-like phenotype. Recently, our group showed that SIN3a (Switch-Independent 3) plays a critical role in the epigenetic regulation of BMPR2 expression in human pulmonary arterial smooth muscle cells (hPASMC). However, our preliminary data suggested that SIN3a regulates BMPR2 expression through a different pathway independently of DNA-methylation in human pulmonary arterial endothelial cells (hPAEC). Methods/Results: We found a significant downregulation of SIN3a expression in the PAEC isolated from PAH patients. In hPAEC, our results showed that SIN3a inhibits cell proliferation, migration and upregulates BMPR2 independently of the methylation status by upregulating the FOXK2 transcription factor. Using a loss-of-function approach using a specific shRNA against FOXK2, we found that the loss of FOXK2 expression using a specific shRNA decreased the expression of BMPR2 in hPAECs. Interestingly, we found that SIN3a overexpression in FOXK2-depleted hPAEC restored the expression of BMPR2. Our results also showed that SIN3a regulates hPAEC proliferation in a FOXK2-dependant manner. Mechanistically, we found that SIN3a interacts physically with FOXK2 to promote its nuclear localization. As a result, we also found enrichment in FOXK2 abundance within the BMPR2 promoter by ChIP-qPCR in PAEC. In vivo , our results showed that restoring SIN3a expression by lentivirus-mediated gene transfer significantly decreased SuHx-induced PAH in mice, as illustrated by decreased vascular remodeling, RV hypertrophy (Fulton index, hypertrophic markers, cardiomyocyte size), and RV systolic pressure. Conclusions: Altogether, our study revealed that SIN3a plays a critical role in the regulation of BMPR2 expression through FOXK2. Additionally, our study identifies lung-targeted SIN3a gene therapy as a new promising therapeutic strategy for treating PAH patients.